1. Field of the Invention
The present invention relates to a low voltage electric appliance, and more particularly to a circuit breaker with a short circuit self-locking function.
2. Description of the Related Art
A circuit breaker, also named an air breaker switch, is composed essentially of a housing, a handle, a self-locking linkage, a tripping linkage, an actuating arm, and a movable contact (see FIG. 1). The work process of this air breaker switch is as described below. The handle controls the self-locking linkage, which causes the actuating arm to move such that the movable contact is forced to abut a metal sheet, thereby closing the circuit. In parallel, the self-locking linkage engages the tripping linkage to achieve self-locking in a closed state (see FIG. 2). To protect the circuit, the prior circuit breaker also has a short circuit actuating mechanism and a bimetal strip protection mechanism provided therein. When the current flowing in the circuit breaker is higher than rated current, usually ten times the assigned current, then a short circuit has occurred. As a consequence, an overcurrent coil of the short circuit actuating mechanism activates a mechanism that drives a actuating arm of the short circuit actuating mechanism to push a lower end of the tripping linkage, which triggers the tripping linkage to pivot such that the self-locking linkage disengages from the tripping linkage, thereby opening the circuit and achieving protection. The work process of the bimetal strip is as follows. When the current flowing in the circuit breaker is higher than the rated current, usually two times the assigned current, the bimetal strip deflects and triggers the tripping linkage to pivot such that the self-locking linkage disengages from the tripping linkage, thereby breaking the circuit and achieving protection. However, the actuating arm of the short circuit actuating mechanism and the bimetal strip will restore their initial states after the circuit breaker has tripped. The above circuit breaker protects the circuit upon occurrence of a short circuit, but a drawback of the design is that the circuit breaker can close again without identifying the reason why the circuit breaker is opened. The operator does not know whether the circuit breaker tripped due to protect against an overcurrent or short circuit. The cause of the accident may persist and worsen, potentially impacting the electrical grid or starting a fire. Such accidents have been reported many times.